Predictions for Neutron Transport in Air, Based on Integral Measurements in Nitrogen and Oxygen at 14 MeV

Using the sphere transmission and time-of-flight techniques, the neutron spectra emitted from 0.58 and 3.0 mfp of nitrogen and from 0.72 mfp of oxygen have been measured for a 14-MeV neutron source. The analysis of the data has been done using the Livermore Monte Carlo Neutron-Transport Program (SORS). Good agreement was obtained for nitrogen with a revised SORS calculation, where five inelastic levels are explicitly included in the computational routine for the (n,n′) cross sections. To obtain agreement between calculations and measurements for oxygen, the computational model had to be extended so that it could account for the presence of inelastic levels. A revision of the cross sections was also carried out. With these new versions of SORS, excellent fits to the experimental measurements for nitrogen and oxygen were obtained. Using the revised SORS program, calculations for the transport of neutrons in air from a 14-MeV point neutron source were obtained.